$0pts$ code:

#include<iostream>
#include<cstdio>
using namespace std;
int n,r;
int m[25];
void print()
{
	for(int i=1;i<=r;i++)
		printf("%3d",m[i]);
	cout<<endl;
	return;
}
void dfs(int step,int k)
{
	if(step>r)
	{
		print();
		return;
	}
	if(k>=n)return;
	for(int i=k;i<=n;i++)
	{
		m[i]=i;
		dfs(step+1,i+1);
		m[i]=0;
	}
	return;
}
int main()
{
	cin>>n>>r;
	dfs(1,1);
	return 0;
}

样例out:

1 2 3
1 2 0
1 2 0
1 0 3
1 0 3
0 2 3
0 2 3

求助各位巨佬qwq